Turbine blade shroud fastening



April 1943. W,IB. FLANDERS 2,315,610

TURBINE BLADE SHROUD FASTENING Filed Jan. 16, 1942 WITNESSES: 4 INVENTOR S g Wnnnsu Bflnnogns.

5 e; 4 BY J a ATTORNEY Patented Apr. 6, 1943 TURBINE BLADE SHROUD FASTENING Warren B. Flanders, Philadelphia, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 16, 1942, Serial No. 426,992

1 Claim.

The invention relates to a row of turbine blades having individual integral shroud elements arranged circumferentially in end-to-end relation to form a shroud construction for the blade passages and wherein the blades are connected in groups by means of shroud bands and tenons extending outwardly from and formed integrally with the shroud elements, the shroud bands contacting with the outer surfaces of the shroud elements, having openings for the tenons, and the tenons being riveted or headed to overlap the bands and hold the latter in place with respect to outer surfaces of the shroud elements, and it has for an object to provide the shroud elements with contiguous flexible end portions to minimize stress concentration in the bands over the contiguous outer corners of the shroud elements.

Due to inevitable small variations in manufacture, the contiguous ends of the shroud elements may be oiiset with the result that, incident to riveting a shroud band in place, the band may bear tightly against an outwardlyprojecting corner or be initially stressed thereby. Furthermore, in operation, the centrifugal and vibratory efiects of the blades may cause corners to act on the bands and over-stress the latter at sections over the corners. To obviate these difficulties, I provide shroud elements with grooves in contiguous ends so as to form tongues which will flex and thereby reduce the band stress. Furthermore, as fiexure of each tongue will occur as arcuate bending thereof, instead of the band stress being concentrated at a limited zone or section, it will be distributed over a substantial length thereof. Also, any rubbing or friction occurring between the bands and the tongues serves to damp vibration. A further object of the invention is to provide a blade shroud construction having these advantageous features.

These and other objects are effected by the invention as will be apparent from the following description and claim taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a fragmentary view, partly in elevation and partly in section and showing a blade row having the improved shroud construction;

Fig. 2 is a fragmentary top plan view of the structure shown in Fig. 1;

Fig. 3 is an elevational View of a blade showing the tie band in section; and,

Figs. 4 and 5 are detail sectional views showing modified forms of shroud elements.

In the drawing, there is shown a row of blades Ill carried by the rotor II and p v With a shroud construction, at l2.

Each blade H3 includes a root element l3, a blade l4 and a shroud element l5. With the blades assembled in a row, the root and shroud elements thereof are disposed circumferentially in end-to-end relation.

The blades are connected in groups by means of tenons l6 and shroud bands II, the tenons being integral with and extending outwardly from the shroud elements, the tie bands having openings it through which the tenons extend, and the tenons being provided with riveted or headed portions l9 which overlap the tie bands and hold the latter firmly in place with respect to the outer surfaces of the shroud elements.

To minimize stress concentrations in the tie bands at sections over contiguous corners of the shroud elements, the latter are formed with flexible tongues engaging the inner surfaces of the bands. While the flexible tongues 20 may be provided in any suitable manner, preferably, the shroud elements have grooves 2! in theiradjacent ends and extending widthwise of the blade row, the grooves being of such depth and located with reference to the outer surface of the shroud elements so as to provide tongues having the required degree of flexibility.

In Fig. 1, the grooves 2| are shaped in cross section so that the tongues 20 taper in section from the groove bottom to the end edge of the shroud element. In Fig. 4;, there is shown the reverse arrangement where the flexible tongues 29a are of substantially uniform thickness; and in Fig. 5, the U-shaped grooves Zlb provide tongues 20a and inner shroud portions 22 each of uniform thickness.

With the structure described, instead of the tie bands being overstressed by continuous corners of the shroud elements, the flexible tongues will bend more or less with the result that the band stress is distributed and stress concentration in a section over a corner is minimized. Furthermore, any friction or rubbing that may occur between the tongues and the inner surfaces of the bands will serve to damp vibration.

While the invention has been shown in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and it is desired, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claim.

What is claimed is:

In a turbine, a row of moving blades defining blade passages, shroud elements integral with the respective blades and disposed circumferentially in end-to-end relation to form a shroud construction covering said blade passages, tenons integral with the shroud elements and extending outwardly therefrom, a plurality of tie bands disposed circumferentially and having openings through which the tenons extend, and rivet heads 10 provided on the tenons and overlapping the tie bands around the openings thereof to retain the tie bands in place with respect to the outer surfaces of the shroud elements, said shroud elements having grooves formed in their circumferentially adjoining ends and extending for the full width thereof to provide outer flexible portions engaging the tie bands and inner portions covering the blade passages.

WARREN B. FLANDERS. 

